Thermomechanical in-plane microactuator

ABSTRACT

A microactuator ( 10 ) providing an output force and displacement in response to an increase in thermal energy is disposed. The microactuator (10) may have a substantially straight expansion member ( 20, 22 ) with a first and a second end. The first end may be coupled to a base ( 12, 16 ) and a second end may be coupled to a shuttle ( 24 ). The expansion member is capable of elongating in a elongation direction. Elongation of the expansion member may urge the shuttle to translate in an output than the elongation direction. In certain embodiments, multiple expansion members are arrayed along one side of the shuttle to drive the shuttle against a surface. Alternatively, expansion members may be disposed on both sides of the shuttle to provide balanced output force. If desired, multiple microactuators may be linked together to multiply the output displacement and/or output force.

1. FIELD OF THE INVENTION

[0001] The present device relates to microelectromechanical systems.More particularly, the device relates to thermally activatedmicroactuators.

2. TECHNICAL BACKGROUND

[0002] Many different transducers have been created to convertelectricity and thermal energy into mechanical force or motion. Forexample, electric linear and rotary motors, relays, and the like areused for many applications. Relays, in particular, are used to carry outfunctions such as valving and switching when actuated by a current.

[0003] However, previously known transducers are typically ill-suitedfor use in microcircuits. Microcircuits are used in many differentapplications, from hearing aids to dog tags, many of which requiresmall-scale mechanical operations. MEMS, or microelectromechanicalsystems, have been developed to provide mechanical operations inmicroscopic environments.

[0004] Nevertheless, known small-scale transducers, or microactuators,are in may respects limited. They are somewhat bulky with respect to thecircuits in which they operate. They also require considerable voltageto operate, and provide only a relatively small amount of mechanicalforce or displacement in return. The high voltage requirements of mostknown transducers make them unusable in CMOS circuits, as found inpersonal computers, which typically operate at 5 Volts or less. Inaddition, known microactuators are often subject to failure due tocontamination, which makes them useless in many exposed environments.Additionally, many known microactuators are inflexible in design, andthus cannot be readily adapted to suit different applications. Knowndevices also must often be manufactured through special processes thatrequire entirely different equipment and procedures from those used toform a circuit.

[0005] One example of a known microactuator is a “U” shaped actuator,with a “hot” arm and a “cold” arm. Both arms have an anchored end and afree end. Each anchored end is fixed to a substrate and the free ends ofthe two arms are connected together by a thin member. The hot arm is arelatively thin member and the cold arm is a relatively thick member.Both arms have a thin flexure near the anchored end. The actuator istriggered by applying an electric current through the actuator, fromanchor to anchor. The thin, hot arm has a higher current density thanthe thick, cold arm, due to its comparatively smaller cross-sectionalarea. The high current density causes the hot arm to heat and expandmore than the cold arm. Because the arms are connected at the free end,the differences in expansion causes the actuator to bend such that thefree end moves along an arc. This actuator functions in a manner similarto a bimetallic strip, in which the different expansion properties ofthe two metals cause the strip to curl. Multiple “U” shaped actuatorsmay be connected to a common actuating structure form an array thatcompounds their output forces. This is accomplished by attaching aflexible yoke between the free end of the actuator and the commonactuating structure. This flexible yoke is required to translate thearc-like motion into a linear actuation.

[0006] While this configuration does provide functional force anddisplacement characteristics, the “U” shaped actuator possesses multipledeficiencies. For example, arc incurred losses during conversion of thearcing output motion into linear translating motion. More specifically,the actuators in the array must expend a portion of their output energyto deform the flexible yokes so that the common actuating structuremoves in a straight line. Additionally, the cold arm's bulky sizeresists deflection as the hot arm arcs towards the cold arm. The forcerequired to bend the cold arm does not contribute to the ultimate outputforce at he “U” shaped microactuator. Furthermore, the cold arm requiresmaterial, volume, and energy but does not contribute to the actuatingforce. The non-contributing material, volume, and energy become evenmore burdensome when multiple “U” shaped actuators are connected to forman array. The flexible yoke members similarly require energy, material,and volume without contributing to the output force produced by theactuator. Thus, the bulk and energy requirements fo the “U” shapedactuator make such actuators unsuitable for certain applications.

[0007] Accordingly, a need exists for a microactuator that can provide ahigh output force and high displacements, while operating at a low inputvoltage. Furthermore, the actuator should be lightweight and small, andshould continue to operate in the presence of contaminants common inmicrocircuit applications. The microactuator should have a flexibledesign that can be easily adapted to suit various input, output, size,and material specifications. Moreover, the microactuator should besimple and easy to manufacture, preferably through methods similar tothose used to make the circuits in which they operate.

BRIEF SUMMARY OF THE INVENTION

[0008] The present micromechanism includes a microactuator that hasadvantageous size, displacement, and force characteristics. Themicromechanism may comprise a generally long and thin expansion memberthat is coupled at a first end to a base member and at a second end to adisplaceable shuttle. In one embodiment, the expansion member extendstowards and the shuttle at an angle slightly offset from a perpendicularattachment to the base member. The expansion member may be configured toelongate in an elongation direction. The shuttle may be configured totravel in an output direction along a single axis. The displaceableshuttle may be constrained such that the lateral distance between thebase member and the axis of shuttle's output direction is fixed. Thisoutput direction is substantially different from the elongationdirection of the expansion member. In one embodiment, the shuttletravels in a direction nearly perpendicular to the elongation directionof the expansion member. The expansion member is comprised of a materialthat can be formed microscopically. The material and shape of theexpansion member may be selected such that substantial elongation occurswhen thermal energy increases in the expansion member.

[0009] Upon an increase of thermal energy within the expansion member,the expansion member elongates in a direction nearly perpendicular tothe base member and shuttle. Since the lateral offset of the base memberand shuttle is constant, the expansion member cannot expandperpendicular to the shuttle. The expansion member's movement at thebase member coupling is limited to slight angular rotation and movementat the shuttle coupling is limited to the uniaxial travel of theshuttle. These limitations may force the expansion member to pivot nearthe base member end and drive the shuttle at the shuttle end. Relativemotion between the base member and the shuttle permits pivoting of theexpansion member such that the increased length of the expansion membercan be accommodated. The result is that a relatively small elongation ofthe expansion member creates a large displacement of the shuttle.

[0010] The microactuators disclosed herein may function substantiallyin-plane, which entails operation of each component within a singleplane. Thus, the microactuator may be made through film depositionmethods similar to those used to construct flat circuits. In fact, amicroactuator according to the invention may even be made simultaneouslyand unitarily with a circuit so that production can be economically andrapidly carried out. The low voltage requirement makes suchmicroactuators operative for CMOS applications and the like, and theirhigh force/displacement characteristics make them uniquely suited toother applications in which efficient motion is desirable. In addition,the simple design of the microactuators of the present invention enablesthem to continue operating even in the presence of small contaminantsoften found in circuit environments.

[0011] The purpose, function, and advantages of the present mechanismwill become more fully apparent from the following description andappended claims, or may be learned by the practice of the invention asset forth hereinafter.

DESCRIPTION OF DRAWINGS

[0012]FIG. 1 is a plan view of one embodiment of a microactuator withhaving symmetrical sets of expansion members configured to drive asingle shuttle;

[0013]FIG. 2 is the plan view of the microactuator of FIG. 1, depictingone possible shape of elongated expansion members and one manner inwhich the microactuator may be connected to receive an electrical input;

[0014]FIG. 3 is a plan view of an alternative embodiment of amicroactuator in which only a single set of expansion members is used;

[0015]FIG. 4 is a plan view of another alternative embodiment of amicroactuator, in which each expansion member has a variable width;

[0016]FIG. 5 is a plan view of another alternative embodiment of amicroactuator, in which two symmetrical sets of expansion members areused, each of which contains two groups of expansion members;

[0017]FIG. 6 is a plan view of an embodiment of an array ofmicroactuator in which two microactuators press inward to amplify themotion of a third microactuator; and

[0018]FIG. 7 is a plan view of another embodiment of an array of themicroactuator, in which two microactuators press inward against ananchored microactuator and an unanchored microactuator to amplify themotion of the unanchored microactuator.

DETAILED DESCRIPTION OF THE INVENTION

[0019] The present device will be best understood by reference to thedrawings, wherein like parts are designated by like numerals throughout.It will be readily understood that the components of the presentmechanism, as generally described and illustrated in the figures herein,could be arranged and designed in a wide variety of differentconfigurations. Thus, the following detailed description of theembodiments of the apparatus and method, as represented in FIGS. 1through 7, are not intended to limit the scope of the claimed mechanism,but are merely representative of present embodiments of the mechanism.

[0020]FIG. 1 depicts a microactuator with enhanced force anddisplacement characteristics. A datum 4 has been established to provideorientation throughout the application. The datum shows negative 5 andpositive 6 X directions (“lateral directions”) and negative 7 andpositive 8 Y directions (“longitudinal directions”). The respectivelocations of the various elements of the microactuator may be moreprecisely defined by referring to the datum 4. The microactuator 10 hasa first base member 12 anchored to a first surface 14 and a second basemember 16 anchored to a second surface. In one embodiment, the surfaces14, 18 may be parts of the substrate of a silicon chip or, in analternative embodiment the surfaces 14, 18 may be parts of one or moreother microelectromechaical mechanisms. Two sets of expansion members20, 22 are coupled to the base members 12, 16 respectively. Theexpansion members 20, 22 may be generally elongated and are composed ofa thermally expanding material. The expansion members 20, 22 extend fromthe base members 12, 16 and are coupled to a shuttle 24 to create aladder shaped actuator.

[0021] The first expansion members 20 are attached to the first basemember 12. The first expansion members 20 extend in the positive Xdirection 6 and are coupled to a side of the shuttle 24. Similarly, thesecond expansion members 22 extend from the second base member 16 in thenegative Y direction 5 and are coupled to the shuttle 24 opposite thefirst expansion members 20. The shuttle 24 may be generally stiff, andmay be slidably disposed on a surface such as a semiconductor substrate.In FIG. 1, the shuttle 24 is only constrained by the expansion members20, 22. The tensile and compressive strengths of the expansion members20, 22 substantially limit the movement of the shuttle to displace inthe positive 8 and negative 7 Y directions. Thus, the lateral distancein the X directions 5, 6 between the base members 12, 16, and theshuttle 24 does not change significantly during operation of theactuator 10. FIG. 1 further depicts the shuttle 24 and base members 12,16 as rectangular in shape, but one skilled in the art will recognizethat these elements may be configured in any number of shapes to fit aparticular design need.

[0022] While FIG. 1 demonstrates a preferred embodiment of presentinvention, an operable microactuator may be formed with a singleexpansion member 20 coupled to a single base member 12 and a shuttle 24.The expansion member 20, the base member 12, and shuttle 24 form an “I”shaped actuator. Thus, any disclosure referring to multiple expansionmembers or groups of expansion members in the application may simply bereplaced with a single expansion member to provide additionalalternative embodiments of the invention. However, even though themicromechanism is operable with only a single expansion member, anincreased number of expansion members will correspondingly increase theoutput force of the device. Thus, the microactuator of FIG. 1 will havea larger output force than an “I” shaped actuator with single expansionmember. This relationship between the output force and the number ofexpansion members provides the microactuator of FIG. 1 with a largevariety of versatile design options. The microactuator 10 can be simplyoptimized by adding or removing expansion members so that themicroactuator 10 only outputs the required force for the actuatingfunction. Thus, the overall size and energy consumption of themicroactuator 10 can be minimalized.

[0023] The individual elements of the ladder shaped actuator 10 in FIG.1 or the “I” shaped actuator described above, which is a subset of themicroactuator 10, maybe attached to each other by multiple methods, suchas chemical or adhesive bonding, integral formation, mechanicalattachment, or the like. In one embodiment, the microactuator 10 is acompliant mechanism. In a compliant mechanism, the base members 12, 16,the expansion members 20, 22, and the shuffle 24 form a singlecontinuous, unitary structure. Compliant mechanisms are a family ofdevices in which flexible and bendable members replace conventionmulti-part devices, such as pin joints. They provide several benefitsincluding simple manufacturing, high strength, and flexibility.Moreover, a compliant mechanism is typically constructed in unitaryfashion. For example, the various components of the embodiment of FIG. 1may be formed from one or more planar layers of polysilicon. The motionof the microactuator 10 is determined by its geometry. Thick members,such as the base members 12, 16 and the shuttle 24, will stay rigid.Conversely, thin or necked-down members, such as the expansion members20, 22, will flex. In FIG. 1, the expansion members 20,22 are thinflexible members; however, where practical, they may be necked-down toform small length flexural pivots to obtain flexibility. Thus, thecompliant nature of the expansion members 20, 22 provides the motion ofthe microactuator 10.

[0024] The expansion members 20, 22 also supply actuating force for themicroactuator 10. The expansion members 20, 22 are preferably made froma material with a high coefficient of thermal expansion (ratio ofthermal expansion to temperature change) to obtain large displacements.However, a material with a lower coefficient or thermal expansion may beused when smaller displacements are desirable. The high coefficientallows for comparatively large elongation of the expansion members 20,22 when the amount of thermal energy increases within the expansionmembers 20, 22.

[0025] When thermal energy increases in the expansion members 20, 22,they elongate. However, as stated above, the lateral distance betweeneach of the base members 12, 16 and the shuttle 24 is fixed.Consequently, as the first expansion members 20 elongate in the positiveX direction 6, the compressive strength of the second expansion members22 prevents the shuttle 24 from moving in the positive X direction 6.Likewise, as the second expansion members 22 elongate in the negative Xdirection 5, the compressive strength of the first expansion members 20prevent the shuttle 24 from moving in the negative X direction 5. Theresult of these constraints is that the expansion members 20, 22 drivesthe shuttle 24 along the Y-axis 7, 8. This biasing occurs as theexpansion members 20, 22 bend or pivot from a first attachment angle 23,to a second attachment angle 21, with respect to the base members 12,16. The first attachment angle 23 may be substantially perpendicular, orclose to 90°. Substantially parallel may be a ±15° offset from a trueperpendicular attachment without diverging from the spirit of theembodiment. The second attachment angle 21 may be somewhat further fromperpendicularity. The trigonometric effect of the decrease in theattachment angle displace the shuttle 24 in the positive Y direction 8so that the expansion member can elongate.

[0026] Applying simple trigonometry to the actuator structure 10 in FIG.1 demonstrates that if the first attachment angle 23 is assumed to benearly perpendicular or close to 90°, then each of the expansion members20, 22 at the second attachment angle 21 will form a hypothenuse of aright triangle in which the non-elongated expansion member 20 or 22 andthe portion or the shuttle 24 between the couplings of the hypothenuse26 or 28 and the non-elongated expansion members 20 or 22 form the othertwo sides of the triangle. The Pythagorean Theorem holds that thehypothenuse 26 or 28 is longer than the adjacent side 20 or 22. Thus, aselongation of the expansion members 20, 22 forces the attachment angleto decrease, the expansion members 20, 22 then move from the adjacentposition of the right triangle to the hypothenuse position 26, 28. Thisangle decrease drives the attached shuttle 24 along the Y-axis 7, 8 to adisplaced position 30. Thus, elongation of the expansion members 20, 22almost completely in the X direction 5, 6 produces a displacement 32 ofthe shuttle 24 in the Y direction 8. Therefore, the elongation directionand the shuttle output direction are substantially different directions.It is important to understand, however, that a substantially differentdirection is not limited to a near 90° difference in directions. Variousembodiments of the microactuator may only require small differences indirection. The difference between the elongation and output directionswill depend on the desired force and displacement characteristics of theactuator.

[0027] An elongation direction that is completely perpendicular to theoutput direction may present some directional control problems; hencesome departure from the perpendicular attachment may be needed. Thus,the incroactuator 10 of FIG. 1 implements an initial angular offset ofthe expansion members 20, 22 to control the actuation direction. Byoffsetting the expansion members 20, 22 such that the first attachmentangle 23 is slightly less than 90°, elongation of the expansion members20, 22 will displace the shuttle 24 in the positive Y direction 8. Whilecomparatively large angle offsets will guarantee a predictabledisplacement direction, positioning the expansion members 20, 22 at anear perpendicular angle provides a greater output displacement 32.

[0028] An advantage of the microactuator 10 over other designs is theability to select a wide range of actuation force and displacementcharacteristics. The largest shuttle displacement occurs when theexpansion members elongate in a direction nearly perpendicular to thedirection of travel of the shuttle 24. However, this displacement comesat the expense of force. The output force can be increased by offsettingthe attachment of the expansion member from a perpendicularconfiguration. The output force will increase as the offset increases,but the displacement distance will correspondingly decrease. Therefore,the first attachment angle 23 may be selected according to the force anddisplacement requirements for the application in which the microactuator10 is to be used. Alternatively, additional expansion members 20, 22 cansimply be added to a microactuator 10 to increase the output force whilemaintaining a desired output.

[0029] A beneficial feature of this design is that a relatively smallelongation of the expansion members 20, 22 can produce a shuttledisplacement over ten times larger than the elongation of the expansionmembers 20, 22. The displacement of the shuttle 24 as a function of theelongation of expansion members 20, 22 can be derived from Pythagoreantheorem, assuming the unelongated expansion members 20, 22 are nearlyperpendicular to the base members 12, 16 and the shuttle 24. As theexpansion members 20, 22 elongate, they depart further fromperpendicularity. The following equation may be used to obtain theoutput displacement of the shuttle 24: and variables are as follows:

Δ={square root}{square root over ((L ₂)²−(L ₁)²)}

[0030] Δ is the displacement of the shuttle 24 in the output direction;

[0031] L₁ is the unelongated length of the expansion members 20, 22; and

[0032] L₂ is the elongated length of the expansion members 20,22.

[0033] This equation measures the length of the unelongated andelongated expansion members as the distance from the base memberattachment to the shuttle attachment. This measurement may vary somewhatfrom the actual length of the expansion member if bending or bucklingoccurs in the member. A ratio (R₁) of displacement to elongation can beobtained through the following equation.$R_{1} = \left( \frac{\Delta}{L_{2} - L_{1}} \right)$

[0034] A more robust equation may also be employed to characterize theoperation of the microactuator 10 without requiring unelongatedexpansion members 20, 22 to have a near perpendicular attachment. Suchan equation may be obtained by referencing the unelongated and theelongated expansion members 20, 22 to theoretical expansion members (notshown) exactly perpendicularly fixed between the base members 12, 16 andthe shuttle 24. The length of this theoretical member is the fixedlateral distance between each of the base members 20, 22 and the shuttle24. This equation provides the output displacement of the shuttle 24 forany of a large range of values of the first attachment angle 23. Theequation and variables are as follows:$\Delta = {\left\lbrack {L_{2} \cdot {\sin \left( {\arccos \left( \frac{L_{0}}{L_{2}} \right)} \right)}} \right\rbrack - \left\lbrack {L_{1} \cdot {\sin \left( {\arccos \left( \frac{L_{0}}{L_{2}} \right)} \right)}} \right\rbrack}$

[0035] Δ is the displacement of the shuttle 24 in the output direction;

[0036] L₀ is the fixed lateral distance between the base member 12 or 16and the shuttle 24;

[0037] L₁ is the unelongated length of the expansion members 20, 22; and

[0038] L₂ is the elongated length of the expansion members 20, 22.

[0039] This equation is derived from the trigonometric relationships oftwo right triangles that share the same base, the common base being thefixed lateral distance (L₀). The physical constraints must be consideredin performing calculations with the above equation. The previousequation functions when the first attachment angle 23 is within 90° ofthe fixed lateral length.

[0040] A shuttle displacement to elongation ratio (R₂) may be calculatedin the same manner as above:$R_{2} = \left( \frac{\Delta}{L_{2} - L_{1}} \right)$

[0041] The previous two equations demonstrate that the displacement ofthe shuttle 12 is more than two times larger than the elongation ofexpansion members 20, 22, even with a first attachment angle 23 lessthan 45°. Although, the highest displacement ratios occur when the firstattachment angle 23 is near 90°, these equations demonstrate that highdisplacement to elongation ratios occur throughout a large range ofvalues of the first attachment angle 23. However, smaller displacementto elongation ratios can also be obtained through application of thepresent invention. Multiple applications may require such smalldisplacements. This discussion is not intended to limit the invention toany displacement to elongation ratio.

[0042] The microactuator 10 may have comparatively low energyconsumption which is due in part to the linear path of the expansionmembers 20, 22. More specifically, each of the expansion members 20, 22has one end coupled to the shuttle 24; these coupled ends move in asubstantially linear path as the microactuator 10 operates. Because themost efficient path between to points is a straight line, the lineartravel of the coupled ends is more efficient than any other path, suchas an accurate, elliptical, or otherwise nonlinear path.

[0043] The substantially straight shape of the expansion members 20, 22may also add to the efficiency of the microactuator 10. Bending consumesenergy; consequently, eliminating bending from a system will increasethe efficiency of the system. Therefore, a generally stiff member ismore efficient than an extremely flexible member. The stiffness (k) of abeam may be calculated using the linear spring constant:$k = \frac{3\quad E\quad I}{L^{3}}$

[0044] k is the stiffness;

[0045] E is Young's modulus, which is a material property;

[0046] I is the moment of area of the cross-section of the beam; and

[0047] L is the beam length.

[0048] Assuming a given cross-sectional moment (I) and a given value ofYoung's modulus (E), the shortest member (L) will be the stiffest.Therefore, because the shortest distance between two points is astraight line, the substantially straight elongation member 20, 22 isthe stiffest and consequently, consumes less energy than a non-straightmember. Stiffness, as discussed above, does not require absoluterigidity, but simply entails sufficient rigidity to substantially avoiddeflection that is not necessary for the motion of a microactuator.

[0049] While FIG. 1 depicts a substantially straight elongated expansionmember 26, 28, this embodiment represents an ideal elongation in whichflexibility is limited to the points at which the expansion members 26,28 are coupled to the base members 12, 16 and the shuttle 24. This idealelongation would require pin joints or necked-down cross-sections thatpermit flexing of the expansion members 20, 22 only at the ends of theexpansion members 20, 22. Maintaining a substantially straight expansionmember may not be as simply accomplished when the expansion member isattached without necked-down section or pivot joints. In a compliantembodiment, in which the base members 12, 16, the expansion members 20,22, and the shuttle 24 are a single continuous device, flexibility atthe attachment points may be low. Therefore, bending at or near theattachment points will not occur as readily. In a member that is fixedon two ends, the most probable location for bending to occur is in thecenter of the member's length, assuming the member has a constantcross-section.

[0050]FIG. 2 shows the microactuator 10 of FIG. 1, with an alternativemode of expansion member elongation. More specifically, the expansionmembers 20, 22 may have elongated configurations 34, 36 respectively.The elongated expansion members 34, 36 may bend in the center duringelongation to for an “S” shape. Despite this flexing, the elongatedexpansion members 34, 36 still remain substantially straight in someaspects. The expansion members 34, 36 remain substantially straight atthe attachment points and only begin to flex near the center of theirlength. Even in the bent region of the “S” shape, the curvature remainsrelatively small. Consequently, the manner in which the expansionmembers 34, 36 bend is more efficient than other bending modes such asarcuate bending, in which a greater degree of bending is present over agreater length. Thus, the microactuator 10 disclosed herein remainsefficient despite some bending.

[0051] The flexure of the “S” shaped expansion members 34, 36 can alsobe understood as an elastically buckling process. As the expansionmembers 20, 22 elongate in the positive X 6 and negative X 5 directionrespectfully, the fixed distance between the base members 12, 16 and theshuttle 24 forces the expansion members 20, 22 to elastically buckle.Elastic buckling is not a permanent deformation of the member; rather,the elongated expansion member 34, 36 temporarily yield under axialloads, but return to their original substantially uneffected state 20,22 when the load is removed. In the embodiment in FIG. 2, the directionof the buckling is controlled by the first attachment angle 23 of theexpansion members 20, 22 with respect to the base members 12, 16. Theelongation and subsequent buckling drive the shuttle 24 in the positiveY direction 8.

[0052] The elongation of the expansion members 20, 22 may be initiatedin a variety of manners. FIG. 2 illustrates that the base members 12,16, have contact surfaces 38, 39, respectively, by which the basemembers 12, 16 are electrically coupled to a current source 37. In oneembodiment, thermal energy in the expansion members 20, 22 is increasedby an electrical current flowing through the expansion members 20, 22from the current source 37. As the current passes through the expansionmembers 20, 22, the electrical resistance of the expansion members 20,22 causes an increase in temperature. The temperature increase causeselongation of the expansion members 20, 22. Thus, in one embodiment ofthe present invention, the shuttle 24 actuates when a current passesthrough the microactuator. Once the current is removed, the amount ofthermal energy decreases to an equilibrium state and the shuttle 24returns to its original position. An increase in the ambient temperaturesurrounding the microactuator 10, may also provide enough thermal energyin the expansion members 20, 22 to actuate the shuttle 24. The ambienttemperature may be increased by disposing a heat generating device nearthe microactuator 10. Other methods of increasing thermal energy withinthe expansion members 20, 22, such as conduction and radiation may alsobe used to actuate the shuttle 24. Additionally, traditional methods ofpreventing heat loss may be implemented in conjunction with themicroactuator 10 to increase efficiency. An adequately insulatedmechanism will require the addition of less thermal energy to provideactuation, and will remain in the actuated position with a lower steadystate current input.

[0053]FIG. 3 demonstrates an alternative embodiment of a microactuator40 according to the invention. The microactuator 40 may have only oneset of expansion members 20. The shuttle 24 directly abuts the secondbase member 42 to restrict motion of the shuttle 24 in the positive Xdirection 6. The second base member 42 is anchored against a surface 44(or another suitable anchoring feature) and in one embodiment, has asmooth surface 46 against which the shuttle 24 slides. The second basemember 42 fixes the lateral distance between the first base member 12and the shuttle 24. Thus, elongation of the expansion members 20 drivethe shuttle in the positive Y direction 8. The microactuator 40 is morecompact than other actuators, such as the microactuator 10, that havetwo sets of expansion members 20, 22. Therefore, the microactuator 40requires less energy to actuate, but has a correspondingly lower outputforce. This embodiment 40 also has an “I” shape. Each of the fourexpansion members 20 forms an “I” shape in conjunction with the basemember 12 and the shuttle 24.

[0054] In another embodiment, the second base member 42, need not be afixed member; it simply must restrain movement of the shuttle 24 in thepositive X direction 6.

[0055] Consequently, a variety of structures may be used in place of thesecond base member 42. In one alternative embodiment, the abuttingsurfaces of the shuttle 24 and the second base 42 may be replaced with arack-and-pinion type structure, so that the shuttle 24 can drive a gearor the like. Alternatively, the second base member 42 may be a membercapable of sliding along the Y axis 7, 8, such as another shuttle 24.The contact surfaces between shuttle 24 and the second base member 42need not be straight surfaces. Various shapes can be implemented thatallow for travel in a combination of X 5,6 and Y 7,8 directions.

[0056]FIG. 4 illustrates an alternative embodiment of expansion memberssuitable for use in any of the microactuator designs of the presentinvention. Each of the expansion members 49 shown here has a variablewidth. The rectangular shapes of the expansion members 49 of FIG. 4represent only one of many possible geometric structures that could beincorporated into the expansion members 49. The variable width geometryof the expansion members 49 may provide structural support so that theexpansion members 49 can be made comparatively long. More specifically,the wide cross-section 48 prevents the expansion member 49 fromplastically buckling, i.e. permanently deforming, when the mechanism isactuated. Additionally, various shaped cross-sections may also serve tocontrol the manner in which the expansion member elastically buckles.

[0057]FIG. 5 shows yet another embodiment of the present invention. Themicroactuator 50 of this embodiment is generally similar to themicroactuator 10 of FIG. 1. However, in the microactuator 50, theexpansion members 20, 22 have been gathered to form groups 52, 54. Theeffect of positioning the expansion members 20, 22 to form the groups52, 54 is to reduce thermal energy losses because the expansion members20, 22 thermally insulate each other. Actuation in a vacuum will alsoreduce energy requirements of a microactuator because thermal energy isnot dissipated by convection. FIG. 5 also demonstrates an angle that hasbeen shown in previous figures. The more accurate attachment clearlydetermines that the displacement direction of the shuttle 24 will be inthe positive X direction 6.

[0058] Referring to FIG. 6, an alternative embodiment shows multiplemicroactuators arrayed to form a single microactuator 60. Thismicroactuator 60 is configured to provide a larger output displacementand/or force than a single microactuator would be capable of providing.FIG. 6 shows two transient microactuators 62 a, 62 b that are similar tothe microactuator 10 depicted in FIG. 1. The first transientmicroactuator 62 a has two base members 64 a, 65 a that may be fixed toa substrate 66. In the embodiment shown, multiple primary expansionmembers 67 a, 68 a are coupled to the base members 64 a, 65 arespectively. As in other embodiments, the actuation direction of thefirst transient microactuator 62 can be controlled by disposing theexpansion members 67 a, 68 a at an offset angle from the base member 64a, 65 a. The embodiment of FIG. 6 shows the expansion members 67 a, 68 acoupled to a transient shuttle 69 a, with the expansion member 67 a, 68a angling toward a biasing actuator 70. The transient shuttle 69 a isdriven in a positive X direction 6 when the expansion members 67 a, 68 aelongate. The transient shuttle 69 a is coupled to a first base member71 a of the biasing actuator 70.

[0059] A second transient microactuator 62 b is coupled to a second basemember 71 b of the biasing actuator 70. Two sets of primary expansionmembers 67 b, 68 b are coupled between two base members 64 b, 65 b and asecond transient shuttle 69 b of the second transient actuator 62 b.Elongation of the primary expansion members 67 b, 68 b drives the secondtransient shuttle 69 b in a negative X direction 8 (the directionopposite the travel direction of the first transient shuttle 69 a). Thedisplacement of the transient shuttles 69 a, 69 b decreases the lateraldistance between the actuating shuttle 77 and base members 71 a, 71 b ofthe actuating shuttle. The decrease in lateral distance drives theactuating shuttle 77 in the Y direction 8. More specifically, the motionof the two transient shuttles 69 a, 69 b forces two sets of secondaryexpansion members 72 a, 72 b to pivot or bend, driving the actuatingshuttle 77 in the positive Y direction 8. Alternatively, the secondaryexpansion members 72 a, 72 b can actuate the actuating shuttle 77 in amanner similar to the expansion members 20, 22 of the microactuator 10of FIG. 1, even if none of the primary expansion members 67 a, 67 b, 68a, 68 b have elongated.

[0060] The largest displacement occurs when all of the expansion members67 a, 67 b, 68 a, 68 b, 72 a, 72 b are simultaneously elongated. Thiswill produce a larger output force and displacement than would bepresent if only the primary expansion members 67 a, 67 b, 68 a, 68 b, orthe secondary expansion members 72 a, 72 b, were utilized. Themicroactuators 10, 40, 50 may be arrayed in various other combinationsto amplify the displacement of a shuttle by using the shuttle of onemicroactuator 10, 40, 50 as a base member attachment for anothermicroactuator 10, 40, 50. The microactuator 50 of FIG. 6 alsodemonstrates that several advantages may be derived from affixing basemembers of a microactuator 10, 40, 50.

[0061] The actuation of the microactuator 60 of FIG. 6 may be controlledthrough selectively applying electric current to the base members 64 a,64 b, 65 a, 65 b, 71 a, 71 b. More specifically, the primary expansionmembers 67 a, 68 a of the first actuator 62 a may be elongated byapplying a current source to the base members 64 a, 65 a. The currentthen flows between the two base members 64 a, 65 a via the expansionmember 67 a, 68 a, to heat, and thereby elongate, the expansion members67 a, 68 a. A similar process may be used to elongate the expansionmembers 67 b, 68 b of the second actuator 62 b. A current source may becoupled to the base members 67 b, 68 b such that the current flowsthrough, heats, and elongates the expansion members 67 b, 68 b.

[0062] The secondary expansion members 72 a, 72 b may be elongated bycoupling a current source to the lower base members 65 a, and 65 b. Thecurrent flowing between the base members 65 a, 65 b similarly flowsthrough, heats, and elongates the expansion members 72 a, 72 b. Thus,three different current sources may be coupled to the microactuator 60to control the energy consumption and actuation sequence. However, asingle current source may alternatively be used to actuate themicroactuator 60 by electrically connecting the two lower base members65 a, 65 b such that current can shunt between the base members 65 a, 65b. This may be accomplished by, for example, replacing the lower basemembers 65 a, 65 b with a single elongated base member 79. A singlecurrent source may then be coupled to the upper base members 64 a, 64 bto actuate the entire microactuator 60. Other current source couplingschemes may be implemented in the microactuator 60 or in othermicroactuator arrays to suit a large variety of control needs.

[0063]FIG. 7 illustrates an alternative embodiment of a microactuator 80that implements multiple microactuators to obtain compound force anddisplacement characteristics. The microactuator 80 is based at least inpart on the sliding microactuator 40 shown in FIG. 3. A first basemember 82 a is fixed to a surface 84 a. At least one primary expansionmember 86 a is coupled to the base member 82 a. The primary expansionmembers 86 a are coupled to a first transient shuttle 88 a. A similarbase member 82 b and expansion member 86 b structure is coupled to asecond transient shuttle 88 b. In one embodiment, the expansion members86 a, 86 b are angled from an orthogonal intersection with the basemembers 82 a, 82 b. The two transient shuttles 88 a, 88 b serve as basemembers for a biasing actuator 89 and an anchoring actuator 90.Secondary expansion members 91 a, 91 b are coupled between the transientshuttles 88 a, 88 b and a biasing shuttle 92. Again, in one embodimentthe secondary expansion members 91 a, 91 b are angled from anperpendicular intersection with the transient shuttles 88 a, 88 b.Secondary, expansion members 94 a, 94 b are also coupled between thetransient shuttles 88 a, 88 b and an anchoring shuttle 96.

[0064] The microactuator 80 functions in a manner similar to the othermicroactuators 10, 40, 50, 60 previously discussed. In one embodiment,the expansion members 86 a, 86 b, 91 a, 91 b, 94 a, 94 b aresimultaneous elongated. The primary expansion members 86 a, 86 belongate, biasing the transient shuttles 88 a, 88 b toward the biasingshuttle 92 and the anchoring shuttle 96. The motion of the transientshuttles 88 a, 88 b compresses the secondary expansion members 91 a, 91b, 94 a, 94 b to transmit the biasing force to the actuating shuttle 92and to the anchoring shuttle 96. The secondary expansion members 91 a,91 b, 94 a, 94 b may simultaneously elongate to partially or fullyresist inward motion of the transient shuttles 88 a, 88 b, and to createadditional biasing force between the actuating shuttle 92 and theanchoring shuttle 96. The secondary expansion members 91 a, 91 b, 94 a,94 b may be made thinner or thicker than the primary expansion members86 a, 86 b to control the proportions of biasing force provided by theexpansion members 86 a, 86 b, 91 a, 91 b, 94 a, 94 b.

[0065] As a result, the actuating shuttle receives force in the positiveY direction 8 and the anchoring shuttle 96 receives force in thenegative Y direction 8. These opposing forces tend to increase thedistance 97 between the biasing shuttle 92 and the anchoring shuttle 96.However, because the anchoring shuttle 96 is fixed in place, theactuating shuttle 92 receives all of the displacement 97. Thus, thecomparatively small force and displacements of the expansion members 86a, 86 b, 91 a, 91 b, 94 a, 94 b in the microactuator 60 may be combinedto create a larger output force and displacement in the actuatingshuttle 92. Similar results, but with a smaller force and displacement,will result if only the primary expansion members 86 a, 86 b areelongated.

[0066] The microactuators disclosed herein may be modified in many otherways to suit a wide variety of applications. The invention may beembodied in other specific forms without departing from its structures,methods, or other essential characteristics as broadly described hereinand claimed hereinafter. The described embodiments are to be consideredin all respects only as illustrative, and not restrictive. The scope ofthe intellectual property rights is, therefore, indicated by theappended claims, rather than by the foregoing description. All changesthat come within the meaning and range of equivalency of the claims areto be embraced within their scope.

1. A microelectromechanical mechanism comprising: a base member; ashuttle; and a substantially straight expansion member attached to thebase member and the shuttle, such that the base member, the shuttle, andthe expansion member substantially form an “I” shape, wherein theexpansion member is configured to elongate in an elongation direction todrive a shuttle in a direction substantially different from theelongation direction.
 2. The microelectromechanical mechanism of claim1, further comprising: a second base member; and a second substantiallystraight expansion member attached to the second base member and theshuttle, such that the second base member, the shuttle, and the secondexpansion member substantially form an “I” shape.
 3. Themicroelectromechanical mechanism of claim 1, wherein the shuttle isconfigured to act as a base member for a second microelectromechanicalmechanism comprising a second shuttle and a second substantiallystraight expansion member wherein a second shuttle of the secondmicroelectromechanical mechanism has an amplified displacement.
 4. Themicroelectromechanical mechanism of claim 1, wherein the shuttle abuts asurface, the surface guiding a direction of travel of the shuttle. 5.The microelectromechanical mechanism of claim 4, wherein the surfacecomprises a plurality of teeth, the shuttle comprising teeth, configuredto mesh with the teeth of the surface.
 6. The microelectromechanicalmechanism of claim 4, wherein the surface is substantially smooth. 7.The microelectromechanical mechanism of claims 1, 2, 3, or 4, whereinelongation of the expansion member is induced by an electrical currentpassing through the expansion member.
 8. The microelectromechanicalmechanism of claims 1 or 4, wherein the fixed base member and theshuttle are electrically coupled to an electrical current source.
 9. Themicroelectromechanical mechanism of claims 2 or 3, wherein at least twobase members are electrically coupled to an electrical current source.10. A microelectromechanical mechanism comprising: a substantiallystraight expansion member comprising a first and a second end; a basemember attached to the first end of the substantially straight expansionmember; and a shuttle attached to the second end of the substantiallystraight expansion member, such that the expansion member is able toelongate in an elongation direction to bias the shuttle in an outputdirection substantially different from the elongation direction.
 11. Themicroelectromechanical mechanism of claim 10, further comprising: asecond base member; and a second substantially straight expansion membercomprising a first end attached to the second base member and a secondend attached to the shuttle.
 12. The microelectromechanical mechanism ofclaim 10, wherein the shuttle is configured to act as a base member fora second microelectromechanical mechanism comprising a second shuttleand a second substantially straight expansion member wherein a secondshuttle of the second microelectromechanical mechanism has an amplifieddisplacement.
 13. The microelectromechanical mechanism of claim 10,wherein the shuttle abuts a surface, the surface guiding a direction oftravel of the shuttle.
 14. The microelectromechanical mechanism of claim13, wherein the surface comprises a plurality of teeth, the shuttlecomprising teeth, configured to mesh with the teeth of the surface. 15.The microelectromechanical mechanism of claim 13, wherein the surface issubstantially smooth.
 16. The microelectromechanical mechanism of claims10, 11, 12, 13, 14, or 15, wherein elongation of the expansion member isinduced by an electrical current passing through the expansion member.17. The microelectromechanical mechanism of claims 10 or 13, wherein thefixed base member and the shuttle are electrically coupled to anelectrical current source.
 18. The microelectromechanical mechanism ofclaims 11 or 12, wherein at least two base members are electricallycoupled to an electrical current source.
 19. A microelectromechanicalmechanism comprising: an expansion member comprising a first end and asecond end; a base member attached to the first end of the expansionmember; and a shuttle attached to the second end of the expansionmember, such that elongation of the expansion member in an expansiondirection induces motion of the shuttle in an output direction, whereinelongation of the expansion member further induces buckling of theexpansion member.
 20. The microelectromechanical mechanism of claim 19,wherein the expansion member is configured to buckle elastically. 21.The microelectromechanical mechanism of claims 19 or 20, wherein theexpansion member is configured to substantially buckle in an “S” shape.22. The microelectromechanical mechanism of claim 19, furthercomprising: a second base member; and a second substantially straightexpansion member comprising a first end attached to the second basemember and a second end attached to the shuttle.
 23. Themicroelectromechanical mechanism of claim 19, wherein the shuttle isconfigured to act as a base member for a second microelectromechanicalmechanism comprising a second shuttle and a second expansion memberwherein a second shuttle of the second microelectromechanical mechanismhas an amplified displacement.
 24. The microelectromechanical mechanismof claim 19, wherein the shuttle abuts a surface, the surface guiding adirection of the travel of the shuttle.
 25. The microelectromechanicalmechanism of claim 24, wherein the surface comprises a plurality ofteeth, the shuttle comprising teeth, configured to mesh with the teethof the surface.
 26. The microelectromechanical mechanism of claim 24wherein the surface is substantially smooth.
 27. Themicroelectromechanical mechanism of claims 19, 20, 22, 23, or 24,wherein elongation of the expansion member is induced by an electricalcurrent passing through the expansion member.
 28. Themicroelectromechanical mechanism of claims 20 or 24, wherein the basemember and the shuttle are electrically coupled to an electrical currentsource.
 29. The microelectromechanical mechanism of claims 22 or 23,wherein at least two base members are electrically coupled to anelectrical current source.
 30. A microelectromechanical mechanismcomprising: an expansion member comprising a first end configured to beattached to a structure and a second end configured to travel in asubstantially linear path during elongation of the expansion member inan expansion direction; and a shuttle connected to the second end suchthat the second end is able to bias the shuttle in an output directionin response to elongation of the expansion member.
 31. Themicroelectromechanical mechanism of claim 30, further comprising: asecond expansion member comprising a first end configured to be fixed inplace and a second end configured to travel in a substantially linearpath during elongation of the second expansion member in an expansiondirection.
 32. The microelectromechanical mechanism of claim 30, whereinthe shuttle is configured to act as a structure to attach a secondmicroelectromechanical mechanism comprising a second shuttle and asecond expansion member wherein a second shuttle of the secondmicroelectromechanical mechanism has an amplified displacement.
 33. Themicroelectromechanical mechanism of claim 30, wherein the shuttle abutsa surface, the surface guiding a direction of travel of the shuttle. 34.The microelectromechanical mechanism of claim 33, wherein the surfacecomprises a plurality of teeth, the shuttle comprising teeth, configuredto mesh with the teeth of the surface.
 35. The microelectromechanicalmechanism of claim 33, wherein the surface is substantially smooth. 36.The microelectromechanical mechanism of claims 30, 31, 32, or 33,wherein elongation of the expansion member is induced by an electricalcurrent passing through the expansion member.
 37. Themicroelectromechanical mechanism of claims 30 or 33, wherein the firstend of the elongation member and the shuttle are electrically coupled toan electrical current source.
 38. The microelectromechanical mechanismof claim 31, wherein the second end of the expansion members areelectrically coupled to a current source.
 39. A microelectromechanicalmechanism comprising: a base member; a shuttle; and an expansion membercomprising a first end and a second end, the first end substantiallyperpendicularly attached to the base member and the second endsubstantially perpendicularly attached to the shuttle, the expansionmember is able to elongate in an elongation direction to bias theshuttle in an output direction substantially different from theelongation direction.
 40. The microelectromechanical mechanism of claim39, wherein the first end is attached to the base member at an angleless than ±15 degrees from exactly perpendicular attachment.
 41. Themicroelectromechanical mechanism of claim 39, further comprising: asecond base member; and a second expansion member comprising a first endsubstantially perpendicularly attached to the second base member and asecond end substantially perpendicularly attached to the shuttle. 42.The microelectromechanical mechanism of claim 39, wherein the shuttle isconfigured to act as a base member for a second microelectromechanicalmechanism comprising a second shuttle and a second expansion memberwherein a second shuttle of the second microelectromechanical mechanismhas an amplified displacement.
 43. The microelectromechanical mechanismof claim 39, wherein the shuttle abuts a surface, the surface guiding adirection of travel of the shuttle.
 44. The microelectromechanicalmechanism of claim 43, wherein the surface comprises a plurality ofteeth, the shuttle comprising teeth, configured to mesh with the teethof the surface.
 45. The microelectromechanical mechanism of claim 43,wherein the surface is substantially smooth.
 46. Themicroelectromechanical mechanism of claims 39, 41, 42, or 43, whereinelongation of the expansion member is induced by an electrical currentpassing through the expansion member.
 47. The microelectromechanicalmechanism of claims 39, or 43, wherein the base member and the shuttleare electrically coupled to an electrical current source.
 48. Themicroelectromechanical mechanism of claims 41, or 42, wherein at leasttwo base members are electrically coupled to an electrical currentsource.
 49. The microelectromechanical mechanism of claims 1, 10, 30, or39, wherein the expansion member is configured to buckle duringelongation.
 50. The microelectromechanical mechanism of claims 1, 10,19, or 39, further comprising a second expansion member connected to thebase member and the shuttle.
 51. The microelectromechanical mechanism ofclaim 50, wherein the second expansion member is disposed substantiallyparallel to the expansion member.
 52. The microelectromechanicalmechanism of claim 51, wherein first and second expansion members aregrouped close together to prevent heat loss.
 53. Themicroelectromechanical mechanism of claims 1, 10, 19, 30, or 39, whereinelongation of the expansion member is induced by an ambient temperatureincrease.
 54. The microelectromechanical mechanism of claims 1, 10, 19,30, or 39, wherein the expansion member has a width that varies along alength of the expansion member.
 55. The microelectromechanical mechanismof claim 54, wherein the expansion member has an increased width of acentral portion of the expansion member.
 56. The microelectromechanicalmechanism of claims 1, 10, 19, 30, or 39, wherein the expansion memberand the shuttle are integrally formed through a single manufacturingprocess.
 57. The microelectromechanical mechanism of claims 1, 10, 19,30, or 39, wherein the expansion member has a material and shapeselected to permit cyclical deflection of the expansion member with nosubstantial plastic deformation of the expansion member.
 58. Themicroelectromechanical mechanism of claims 1, 10, 19, or 39, wherein thebase member is at a fixed place.
 59. The microelectromechanicalmechanism of claim 58, wherein the base member is affixed on a siliconwafer.
 60. The microelectromechanical mechanism of claim 58, wherein thebase member is affixed to another microelectromechanical mechanism. 61.The microelectromechanical mechanism of claims 1, 10, 19, 30, or 39,wherein the expansion member is configured to actuate the shuttle whenthermal energy in the expansion member decreases.
 62. Amicroelectromechanical mechanism comprising: an expansion membercomprising a first and a second end; a base member coupled to the firstend of the expansion member; and a shuttle coupled to the second end ofthe expansion member such that the expansion member is able to elongatea first distance, wherein the elongation of the expansion member biasesthe shuttle a second distance in an output direction, and wherein thesecond distance is at least 1.5 times larger then the first distance.63. A microelectromechanical mechanism comprising: a generally linearexpansion member comprising a first end and a second end; a base membersubstantially perpendicularly coupled to the first end of the expansionmember; and a shuttle substantially perpendicularly coupled to thesecond end of the expansion member, wherein the shuttle is configured tomove in an output direction with a displacement substantiallycharacterized by the function: Δ={square root}{square root over ((L₂)²−(L ₁)²)} wherein: Δ is the displacement of the shuttle in the outputdirection; L₁ is the unelongated length of the expansion member; and L₂is the elongated length of the expansion member.
 64. Amicroelectromechanical mechanism comprising: an expansion membercomprising a first end and a second end; a base member coupled to thefirst end of the expansion member; and a shuttle coupled to the secondend of the expansion member, wherein the shuttle is configured to movein an output direction with a displacement substantially characterizedby the function:$\Delta = {\left\lbrack {L_{2} \cdot {\sin \left( {\arccos \left( \frac{L_{0}}{L_{2}} \right)} \right)}} \right\rbrack - \left\lbrack {L_{1} \cdot {\sin \left( {\arccos \left( \frac{L_{0}}{L_{2}} \right)} \right)}} \right\rbrack}$

wherein: Δ is the displacement of the shuttle in the output direction;L₀ is the fixed lateral distance between the base member and theshuttle; L₁ is the unelongated length of the expansion member; and L₂ isthe elongated length of the expansion member.
 65. Amicroelectromechanical mechanism comprising: a first base member; asecond base member; a third base member; a fourth base member; aplurality of primary expansion members each of which is configured toelongate in an elongation direction in response to an increase ofinternal thermal energy; a first transient shuttle configured such thatat least one primary expansion member is coupled between the first basemember and the first transient shuttle and at least one primaryexpansion member is coupled between the second base member and the firsttransient shuttle, the primary expansion members are positioned to biasthe first transient shuttle to translate in a direction substantiallydifferent from the elongation direction of the primary expansionmembers; a second transient shuttle configured such that at least oneprimary expansion member is coupled between the third base member andthe second transient shuttle and at least one primary expansion memberis coupled between the fourth base member and the second transientshuttle, the primary expansion members are positioned to bias the secondtransient shuttle to translate in a direction substantially differentfrom the elongation direction of the primary expansion members; aplurality of secondary expansion members each of which is configured toelongate in an elongation direction in response to an increase ofinternal thermal energy; and an actuating shuttle configured such thatat least one secondary expansion member is coupled between the actuatingshuttle and the first transient shuttle and at least one secondaryexpansion member is coupled between the actuating shuttle and the secondtransient shuttle, the secondary expansion members are positioned tobias the second transient shuttle to translate in a directionsubstantially different from the elongation direction of the primaryexpansion members;
 66. The microelectromechanical mechanism of claim 65wherein the actuating shuttle is configured to displace an additionalmicroactuator device.
 67. The microelectromechanical mechanism of claim65 wherein any two mounting members not coupled directly to the sametransient shuttle are electrically coupled to a current source.
 68. Themicroelectromechanical mechanism of claims 65, 66, or 67, whereinelongation of the primary and secondary expansion members is induced byan electrical current passing through the expansion member.
 69. Themicroelectromechanical mechanism of claims 65, 66, or 67, wherein atleast two of the base members are electrically coupled to a currentsource.
 70. The microelectromechanical mechanism of claim 69 wherein thesecond and third base members are electrically coupled to a currentsource.
 71. The microelectromechanical mechanism of claim 65 wherein theprimary expansion members are configured to move the actuating shuttleindependent of the secondary expansion members.
 72. Themicroelectromechanical mechanism of claim 65, wherein the secondaryexpansion members are configured to move the actuating shuttleindependent of the secondary expansion members.
 73. A method foractuating a micromechanism, the micromechanism comprising an expansionmember having a first end coupled to a base member and a second endcoupled to a drivable shuttle, the method comprising: elongating theexpansion member in an elongation direction; elastically buckling theexpansion member against the shuttle; applying a biasing force resultingfrom buckling of the expansion member to the shuttle, a portion of thebiasing force urging the shuttle in a direction substantially differentfrom the elongation direction.
 74. A method for actuating amicromechanism, the micromechanism comprising an expansion member havinga first end coupled to a base member and a second end coupled to adrivable shuttle, the method comprising: providing an energy source; anddisposing the energy source in communication with the expansion memberto elongate the expansion member such that the expansion member bucklesto bias the shuttle in an output direction substantially different fromthe elongation direction.
 75. A method for actuating a micromechanism,the micromechanism comprising an expansion member having a first endcoupled to a base member and a second end coupled to a drivable shuttle,the method comprising: disposing the base member and shuttle such that alateral distance between the base member and the shuttle remainssubstantially fixed; elongating the expansion member in an elongationdirection a first distance; and biasing the shuttle a second distance inan output direction, the second distance being 1.5 times larger than thefirst distance.
 76. A method for actuating a micromechanism, themicromechanism comprising an expansion member, a base member, and adrivable shuttle, the method comprising: fixing a lateral distancebetween the base member and the shuttle; disposing the expansion membersubstantially perpendicular to the base member and the shuttle; andelongating the expansion member such that the expansion member pressesagainst the shuttle, the expansion member moving from a substantiallyperpendicular disposition to displace the shuttle.